The prior art has established countless methods of preparing potassium sulfate. Typical of the known methods is exemplified by U.S. Pat. No. 4,588,573, issued May 13, 1986, to Worthington et al. In this reference, potassium chloride and sulfuric acid are reacted. Although meritorious, the method requires sulfuric acid which is generally expensive and requires special conditions for handling.
The co-production of potassium sulfate, sodium sulfate and sodium chloride is taught in U.S. Pat. No. 5,552,126, issued to Efraim et al., Sep. 3, 1996. Progressive precipitations with an evaporation step are requisite for the process. As is well known in chemical process design, costly energy consuming unit operations add to the overall operating expenses for the process which are translated to the profit margin. Accordingly, it is most desirable to avoid such operations in processes.
U.S. Pat. No. 5,549,876, issued Aug. 27, 1996, to Zisner et al., provides methodology for potassium sulfate production involving differential contacting. Potash, water and sodium sulfate are placed in a differential countercurrent contactor to produce the potassium sulfate.
Potassium chloride and sulfuric acid are reacted and the resulting mixture kneaded to produce potassium sulfate, as disclosed by Iwashita et al., in U.S. Pat. No. 4,342,737, issued Aug. 3, 1982.
Other methods of manufacture include fractional crystallization of sulfate ores or by the Hargreaves process.
It would be most desirable for potassium sulfate production to be achieved without the use of acids, high energy input or other such unit operations. The present invention provides for such a process.